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Insight - How DC Motor Works

Written By: 

Ashok Sharma
DC Motors convert electrical energy (voltage or power source) to mechanical energy (produce rotational motion). They run on direct current. The Dc motor works on the principle of Lorentz force which states that when a wire carrying current is placed in a region having magnetic field, than the wire experiences a force. This Lorentz force provides a torque to the coil to rotate.
DC Motor
Fig. 1: Image Showing Commonly used DC Motor
A commonly used DC Motor is shown in the image above.

PCB & Brushes

DC Motor PCB
Fig. 2: Motor Speed Conrol Circuit Located on Back Side of DC Motor
On opening the back cover of the motor you can have a look to the motor speed control circuit from behind.
DC Motor Brushes
Fig. 3: DC Motor Brushes that Takes Input Current to Coil
The above image shows the brushes of the DC motor which helps the motor to take input current to the coil. The brushes always remain connected with any two commutators and supplying the input current to the coil while it is rotating.

Coil Arrangement

DC Motor Coil Arrangement
Fig. 4: Image Showing Electrical Coil Arrangement in Magnet
You can have a closer look as to how the electrical coil is arranged in the permanent magnet.
DC Motor Coils
Fig. 5: Arrangement of Magnet, Coil, and Metal Plates of DC Motor
When DC current is passed through the coil, it works as electromagnet. As you can see the iron plates attached around the coil helps the coil to keep in center and movable. Permanent magnet attracts these three iron plates equally; resultantly it stays in the center of the permanent magnet.

Permanent Magnet & Circuitry

DC Motor Permanent Magnet
Fig. 6: Image Showing Three Commutators that are Connected to Coil
There are three commutators shown in the image. Each one is directly connected with the coil to supply the current in.
Permanent Magnet Arrangement in DC Motor
Fig. 7: Image of DC Motor Magnet
The permanent magnet is cascaded in the body of the motor. The coil working as electromagnet moves in the magnetic field of this magnet.
Circuitry in DC Motor
Fig. 8: IC that Controls Motor Speed of DC
A motor speed control IC is used to control the rotating speed of compact DC motor. The IC integrated in the circuit has an inbuilt reverse voltage protection circuit.
Working: As we have discussed, DC motor work on Lorentz force concept. When we pass the input DC current to the coil through the brushes, it directly goes to the coil inside the motor body. This makes coil to work as an electromagnet. Magnetic fields of both magnets interact with each other that results in a force which in turn produces the necessary torque required to move the coil. This torque drives the coil to move round and a shaft attached with the coil moves too.


The explanation is very helpful.